A COD value and COD load calculation method was determined using the intensive measurement results of COD values and flow rates in the Kinokawa river. For 4 years, hourly measurements lead COD values changed with flow rate. The relation between flow rates and COD values was analyzed. Using this relation, past COD values and COD loads could easily be calculated from flow rate. The used data has no data of high flow rate condition because sampling is difficult at the condition of high flow rate. With the exclusion of high flow rate (more than 1400m3/s), the calculation results were in good agreement with actual measurements. The estimated past COD loads of the Kinokawa River were very changeable and maximum COD loads reached 8 times that of minimum values for past 29 years.
